Fey Ancestry. Zabbas (Possessed) has advantage on saving throws against being charmed, and magic can't put Zabbas to sleep. 

Brave. Zabbas (Possessed) has advantage on saving throws against being frightened.

Brute. A melee weapon deals one extra die of its damage when Zabbas (Possessed) hits with it (included in the attack).

Spellcasting. Zabbas (Possessed) is a 7th-level spellcaster. His spellcasting ability is Intelligence (spell save DC 16, +8 to hit with spell attacks). Zabbas has the following wizard spells prepared:

Cantrips (at will): fire bolt, light, mage hand, prestidigitation
1st level (4 slots): burning hands, magic missile, shield
2nd level (3 slots): scorching ray
3rd level (3 slots): counterspell, fireball, lightning bolt
4th level (1 slot): fire shield, stoneskin*

*Zabbas (Possessed) casts these spells on himself before combat.

Multiattack. Zabbas (Possessed) makes two melee attacks and casts a cantrip or makes 3 Deer Claw attacks.

Rapier. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 14 (2d8 + 5) piercing damage plus 3 (1d6) psychic damage.

Deer Claw. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit:  12 (2d6 + 5) slashing damage.

Fire Bolt (Cantrip). Ranged Spell Attack: +8 to hit, range 120 ft., one target. Hit: 11 (2d10) fire damage.

Horrid Scream (Recharge 5-6). Zabbas (Possessed) shoots a dark beam from the center of its antlers in a 60-foot line that is 5 feet wide. Each creature in that line must make a DC 16 Dexterity saving throw, taking 44 (8d10) necrotic damage on a failed save, or half as much damage on a successful one.

Magical Wilting (Once Only). Zabbas (Possessed) chooses one creature it can see within 60 feet of it. If they do not have a magic circulator, they must roll a d20, on a 5 or lower they fail, DC 6 any roll higher they succeed.. On a failure their magic item is destroyed and ripped apart, on a successful save nothing happens to the magic item. This attack as no effect of Armaments of Myth.

Zabbas Sagewood (Possessed) has 3 legendary actions that he recovers at the start of his turn.

Rapier Attack (Costs 1 Action). Zabbas one rapier or deer claw attack.

Spellcasting (Costs 2 Actions). Zabbas casts a spell from his spell list.

Trauma Response (Costs 2 Actions) Zabbas reaches into the mind of a creature with 60 ft. of him. The creature must make a DC 17 Wisdom Saving Throw or become incapacitated for 1 minute. The target is brought into their mind to relive a exaggerated version of possible trauma or insecurities they may have. Fighting against the trauma they creature can make another wisdom saving throw at the end of their turn.